1. Field
The present disclosure relates to a heat exchange apparatus, and more particularly, to a heat exchange apparatus which can be used in a ventilation system.
2. Discussion of the Related Technology
As recent buildings have become many-storied and airtight through the development of construction techniques, natural introduction of fresh outdoor air into rooms is intercepted and thus indoor air pollution levels increase, resulting in negative health influences on persons residing in such buildings. One of the best ways is to introduce a large amount of fresh outdoor air into rooms through active ventilation. However, additional energy costs for heating, humidifying, cooling and dehumidifying the air to be introduced into the rooms may be incurred to properly maintain the temperature and humidity of the indoor air.
A heat exchanging ventilator is a ventilator equipped with a heat exchange apparatus for transferring thermal energy from hot air to cold air, wherein polluted indoor air is exhausted to the outside and fresh outdoor air is introduced into a room while thermal energy included in the hot air is recovered and then transferred to the cold air. Therefore, this heat exchanging ventilator is usefully employed due to saving of additional energy costs incurred during ventilation. Heat exchangers for use in an exemplary heat exchanging ventilators are classified into a plate type heat exchange apparatus and a rotary type heat exchange apparatus according to heat exchanging manners.
FIG. 1 shows an example of an exemplary heat exchanging ventilator, which is equipped with a plate type heat exchange apparatus. Referring to FIG. 1, a heat exchanging ventilator 10e comprises a case 11e, a plate type heat exchange apparatus 20e, four partition walls 12e, 13e, 14e and 15e, an exhaust blower 16e, and an intake blower 17e. Referring to FIGS. 1 and 2, the plate type heat exchange apparatus 20e has a hexahedral shape and is constructed of multiple layers. Each layer has a plurality of long, narrow channels through which air passes, and channels in odd-numbered layers and channels in even-numbered layers are arranged to extend in directions orthogonal to each other. Referring to FIG. 1, the plate type heat exchange apparatus 20e is positioned at the center of the interior of the case 11e. The four partition walls 12e, 13e, 14e and 15e extend from four side edges of the heat exchange apparatus 20e to partition the interior of the case 11e into four spaces. Two diagonally positioned spaces of the four spaces formed in the case 11e communicate with each other through the heat exchange apparatus 20e. The exhaust blower 16e and the intake blower 17e are installed respectively in two adjacent spaces of the four spaces formed in the case 11e. In such a configuration, if the exhaust blower 16e and the intake blower 17e are operated, ventilation is achieved in such a manner that a cold intake air stream 21e receives thermal energy from a hot exhaust air stream 19e while passing through the long, narrow channels of the plate type heat exchange apparatus 20e and is then introduced into a room as a hot intake air stream 18e, whereas the hot exhaust air stream 19e transfers the thermal energy to the cold intake air stream 21e while passing through the long, narrow channels of the heat exchange apparatus 20e and is then exhausted outdoors as a cold exhaust air stream 22e. The temperature exchange efficiency of the plate type heat exchange apparatus 20e is determined depending on length L, height H, the sectional shape and size of a channel, and a flow rate through the channel, which are illustrated in FIG. 2, and moisture included in air is not exchanged.
The ventilator employing the plate type heat exchange apparatus has a temperature exchange efficiency of about 70% to 80% and an enthalpy exchange efficiency of about 40% to 50%, and has a simpler structure and a higher degree of freedom in view of design for its appearance and can be more slimly designed compared with a ventilator employing a rotary type heat exchange apparatus. Thus, a ventilator employing a plate type heat exchange apparatus can be applied to a small-sized heat exchanging ventilator. However, since moisture included in the air is not exchanged during heat exchange, the air 18e introduced into the room is dry and the ventilator employing the plate type heat exchange apparatus has a relatively low enthalpy exchange efficiency, which is a barometer of energy savings, as compared with a ventilator employing a rotary type heat exchange apparatus, resulting in lowered usefulness thereof. In addition, if dust included in the outdoor intake air stream 21e and the indoor exhaust air stream 19e, which are introduced into the ventilator 10e, is deposited in the long, narrow channels formed in the heat exchange apparatus 20e, the temperature and enthalpy exchange efficiencies are lowered and the flow rate is abruptly decreased. Thus, the heat exchange apparatus 20e should be periodically cleaned during usage. However, since it is difficult to clean out dust deposited in the long, narrow channels, the heat exchange apparatus should be frequently replaced after use for a certain period of time. This becomes a cause of serious deterioration of the economic efficiency of the heat exchanging ventilator.
FIG. 3 shows another example of an exemplary heat exchanging ventilator, which is equipped with a rotary type heat exchange apparatus. Referring to FIG. 3, a heat exchanging ventilator 10f comprises a case 11f, a rotary type heat exchange apparatus 20f, an exhaust blower 16f, and an intake blower 17f. Referring to FIGS. 3 and 4, the rotary type heat exchange apparatus 20f has a rotating wheel 24f containing a heat exchanging medium or heat exchanger 23f and the interior thereof is partitioned into four regions by first and second partition walls 12f and 13f crossing each other. The rotating wheel 24f is installed on the first partition wall 12f such that a rotational axis thereof is perpendicular to the first partition wall 12f, and the rotating wheel is rotated by means of a motor 25f and a power transmission device 26f. The interior of the case 11f is partitioned into the four spaces by means of the two partition walls 12f and 13f. The exhaust blower 16f and the intake blower 17f are installed respectively in two diagonally positioned spaces of the four spaces formed in the case 11f. Referring to FIGS. 3 and 5, a hot exhaust air stream 19f transfers thermal energy and moisture to a portion of the heat exchanging medium 23f while passing through the heat exchanging medium 23f and is then exhausted outdoors as a cold exhaust air stream 22f, whereas the portion of the heat exchanging medium 23f, which has received the thermal energy and the moisture from the hot exhaust air stream 19f, is rotated together with the rotating wheel 24f and comes into contact with a cold intake air stream 21f. The cold intake air stream 21f receives the thermal energy and moisture from the heat exchanging medium 23f while passing through the portion of the heat exchanging medium 23f, which has received thermal energy and moisture from the hot exhaust air stream 19f, and is then introduced into a room as a hot intake air stream 18f. A ventilator employing such a rotary type heat exchange apparatus has a temperature exchange efficiency of about 80% to 95% and an enthalpy exchange efficiency of about 60% to 75%. Since the moisture included in the air is exchanged together with the thermal energy during heat exchange contrary to a ventilator employing a plate type heat exchange apparatus, the air introduced into the room is less dry and the enthalpy exchange efficiency that is a barometer of energy savings is relatively higher as compared with a ventilator employing a plate type heat exchange apparatus, resulting in increased usefulness thereof. On the other hand, since the intake blower 17f and the exhaust blower 16f should be positioned on both sides of the rotating wheel 24f, this ventilator is relatively bulkier than a ventilator employing a plate type heat exchange apparatus. In addition, since the heat exchanging medium 23f is fixed to the disk-shaped rotating wheel 24f, the degree of freedom in view of design for its appearance is decreased. Thus, a ventilator employing a rotary type heat exchange apparatus is mainly used as a large-sized heat exchanging ventilator.
In addition, a ventilator employing a rotary type heat exchange apparatus suffers from decrease in the efficiency due to air leakage. This is shown in FIG. 5. Referring to FIG. 5, since heat and moisture are transferred while the rotating wheel 24f is rotated, gaps exist between the rotating wheel 24f and the two partition walls 12f and 13f, and air leaks through the gaps. An axial leaking air stream 27f generated through the gap between the first partition wall 12f and the rotating wheel 24f is a cause of deterioration of heat exchange efficiency, and an indoor-side leaking air stream 28f of two radial leaking air streams 28f and 29f generated through the gaps between the second partition wall 13f and the rotating wheel 24f, becomes mixed, as a portion of the polluted exhaust air stream 19f, with the indoor intake air stream 18f and then introduced into the room again. Thus, the leaking air stream 28f is a cause of reduction in a net intake air stream. Thus, the amount of radial leaking air stream 28f is limited to less than 10%, which causes additional production costs and power loss in operation. Thus, this ventilator has limited applications in spite of its better heat exchange efficiency than that of a ventilator employing a plate type heat exchange apparatus.
As for the heat exchanging medium for use in the rotary type heat exchange apparatus, there have been developed more efficient and reasonable heat exchanging media to improve thermal energy and moisture exchange efficiencies and to reduce pressure loss generated when air passes through the heat exchanging media. U.S. Pat. No. 4,497,361 discloses a structure capable of automatically cleaning a heat exchanging medium, wherein suitable porosity is kept by incorporating a network structure made of plastic or metal wires coated with a moisture absorbent into a disk. U.S. Pat. No. 4,093,435 discloses a honeycomb structure, wherein multiple layers of a corrugated cardboard with a specific composition, density and thickness are formed in a wheel to make a plurality of parallel passages in a flowing direction of air.
However, such heat exchanging media having a network structure and a honeycomb structure are easily contaminated in use due to impurities included in the air, and they have difficulty in disassembling the heat exchanging media contained in the rotating wheel and cleaning and assembling the heat exchanging media subsequently. In particular, a small-sized rotary type heat exchange apparatus has serious difficulty in dissembling, cleaning and assembling a contaminated heat exchanging medium. Thus, this is a cause of difficulty in applying a rotary type heat exchange apparatus to a small-sized heat exchanging ventilator. Furthermore, since the heat exchanging medium formed of the corrugated cardboard disclosed in U.S. Pat. No. 4,093,435 is rolled around the wheel, it is impossible to dissemble and assemble the heat exchanging medium. In addition, since the heat exchanging medium suffers from changes in length and thence in shape due to the variance of temperature, the durable life of the heat exchange apparatus is eventually shortened.
Recently, in order to complement the disadvantages of the heat exchanging medium with the network structure or honeycomb structure, U.S. Pat. No. 5,069,272 discloses random matrix media constructed of a plurality of connected heat-containing fibrous materials with small diameters. These random matrix media have interconnections mainly achieved by mechanical means such as needle punching, and can be easily attached to and detached from a wheel that is partitioned into one or more regions. Thus, the random matrix media have advantages in that they can be easily cleaned and made into a slimmer configuration. However, during a ventilating operation, the materials in the form of staples interconnected through needle punching are separated and then mixed with and floated in an air stream introduced into a room. Further, the materials in the form of staples are separated and lost during cleaning. Thus, it has been revealed that it is difficult to keep the original heat and moisture exchange efficiencies and the random matrix media are compressed to represent a remarkable decrease in its porosity after use for a long time, thereby increasing resistance against an air stream.
The foregoing discussion is to provide general background information, and does not constitute an admission of prior art.